Climate Change in the Arctic - The Changing Arctic Environment: The Arctic Messenger - page 298

ate and an increase in acidity of 0.4 pH may occur. Will organisms be able to adapt to
these changes in such a short time frame and what will be the impact on the marine eco-
system if such fundamental food web building blocks as planktonic coccolithophores are
significantly less productive? Some marine animals with shells have always occupied wa-
ters where Ω arag or Ω cal is <1.0. They can do this because building and maintaining their
skeletal structures is a continuous and dynamic process. However, it requires the expense
of devoting more energy to this task as against, for example, reproduction. Therefore, ad-
aptation may be feasible, but whether it can happen given the rate of change is unknown.
AMAP completed an Arctic Ocean Acidification Assessment in May 2013. It was a
difficult task because there is so little Arctic information available. Nevertheless, the as-
sessment showed that the Arctic region is subject to the same overall trend towards acidi-
fication that is occurring elsewhere around the world, which leads to a lowering of pH from
the former global mean of about 8.16. The assessment reported that in the Barents Sea and
around Iceland, seawater pH has been declining at a rate of about 0.02 per decade since the
late 1960s. However, once again, the Arctic and Antarctic ecosystems have been singled
out by nature for special treatment of the kind we would rather not see. These two ecosys-
tems are preconditioned to be especially vulnerable to acidification. This is taking place
because a number of natural conditions and processes are amplifying the ocean acidifica-
tion in the Arctic. First, pH decreases with temperature and Arctic waters are cold. Second,
the Arctic Ocean receives a great deal of freshwater that has a highly variable pH, but it is
always less than that of seawater and generally has a lower alkalinity (ability to resist pH
change upon addition of free hydrogen ions). Also, remember the freshwater that results
from melting sea ice and that a huge accumulation of freshwater is presently sitting in the
Beaufort Sea. Other processes, such as the nature of coastal erosion, the location of rivers
carrying organic matter and sediment and seasonality, all result in a complex pattern where
acidification is not uniform across the circumpolar Arctic seas.
How these all conspire together has been studied in some detail on the coastal shelves
around Alaska, especially in the Bering and Chukchi seas.